Liquid fuel pumping apparatus

ABSTRACT

A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and including an injection pump including a member movable by a piston to vary the timing of injection of fuel, the piston containing a servovalve, one end of which is subjected to a first fluid pressure dependent upon the speed at which the apparatus is driven, and the other end of which is subjected to a second fluid pressure which varies in accordance with the load on the associated engine, the servovalve acting to control the fluid pressure applied to the piston.

United States Patent Inventor Appl. No.

Filed Patented Assignee Priority LIQUID FUEL PUMPING APPARATUS 1 Claim, 4 Drawing Figs.

US. Cl 123/139,

417/218, 4l7/206(Disil), 4 l 7/253(Disil) Int. Cl L02m 39 09 Field ofSearch 103/2, 37;

Primary Examiner-William L. Freeh Attorney-Holman, G1ascock, Downing and Seebold ABSTRACT: A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and including an injection pump including a member movable by a piston to vary the timing of injection of fuel, the piston containing a servovalve, one end of which is subjected to a first fluid pressure dependent upon the speed at which the apparatus is driven, and the other end of which is subjected to a second fluid pressure which varies in accordance with the load on the associated engine, the servovalve acting to control the fluid pressure applied to the piston.

' Pmmem 5m 3552.366

SHEET 1 OF 2 BNVENTOR ATTORNEYS PATENTEU JAN 5 mm SHEET 2 BF 2 I FICA.

INVE NTOR ATTORNEYS LIQUID FUEL PUMPING APPARATUS This invention relates to liquid fuel pumping apparatus for supplying fuel to internal combustion engines and of the kind comprising in combination, an injection pump including a member adjustable to control the timing of injection of fuel to the engine, a fluid pressure operable piston for determining the setting of said member, a resiliently loaded servovalve for controlling the fluid pressure applied to said piston and means for applying to the servovalve in opposition to the force exerted by its spring, a first fluid pressure dependent upon the speed at which the apparatus is driven.

The object of the invention is to provide such an apparatus in a simple and convenient form.

According to the invention an apparatus of the kind specified includes additional means to provide a second fluid pressure which is dependent upon the load applied to the engine, said second fluid pressure being applied to the servovalve to assist the action of the spring whereby the setting of the piston is depended upon the speed of and the load applied to the engine.

ln the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a liquid fuel pumping apparatus in accordance with the invention;

FIG. 2 is a section on the line 2-2 of FIG. 1;

FIG. 3 is a sectional plan view to an enlarged scale of part of the apparatus of FIGS. 1 and 2; and

FIG. 4 shows a fluid circuit diagram of the apparatus.

Referring to FIG. 1 there is provided a body part 1 in which is mounted a rotary cylindrical distributor member 2 having formed at one end a head 3 in which is formed a transverse bore 4 mounting a pair of reciprocable pumping plungers 9. The pumping plungers are arranged to be moved inwardly as the distributor member is rotated, by the action of a plurality of cam lobes formed on the internal periphery of an annular cam ring 15 which surrounds the distributor member at this point. Also formed in the distributor member is a longitudinal bore which at one point is in communication with an outwardly extending delivery passage 17 which is arranged to register in turn and as the distributor member rotates, with a plurality of outlet ports 18 which in use, are connected to injection nozzles mounted on the associated engine.

At another point the longitudinal passage is in communication with a plurality of equiangularly disposed and radially extending inlet passages 11 which register in turn, as the distributor member rotates with an inlet port 12 formed in the body part. The communication between an inlet passage 11 and the inlet port 12 occurs during the time when the plungers 9 are permitted to move outwardly by the cam lobes and the communication of the delivery passage 17 with one of the outlet ports 18 occurs during inward movement of the plungers.

At the opposite end of the distributor member to the transverse bore, is mounted the rotor of a vane-type feed pump 5 having an inlet 6 and outlet 7 in the body part. The inlet 6 of the feed pump is in use, connected to a-source of liquid fuel and the inlet and outlet are interconnected by way of valve means 8 which controls the output pressure of the feed pump in such a manner that it varies in accordance with the speed at which the apparatus is driven. Since the distributor member is driven by the engine, the output pressure of the feed pump is also dependent upon the speed at which the engine is driven. The outlet of the feed pump is in communication with the aforesaid inlet port by way of a passage formed in the body part and this passage is provided with a throttle valve 14 whereby the quantity of fuel which flows through the inlet port 12 whilst the plungers are capable of moving outwardly can be varied. The throttle valve consists of an angularly adjustable cylindrical member the setting of which is controlled by a speed-sensitive governor (not shown).

The cam ring 15 is angularly adjustable within the body part about the axis of rotation of the distributor member 2 and in this manner variation in the timing of injection of fuel to the engine can be efi'ected. For adjusting the setting of the cam ring a fluid pressure operable piston 19 is provided and this is located within a cylinder 20 which is disposed tangentially relative to the cam ring. The piston is connected to the cam ring by means of a radial peg secured to the latter and engaged within a recess formed in the piston. Moreover, the piston is loaded by means of a coiled compression spring 21 towards the retarded position.

Formed in the piston is an axially extending bore 22 in which is slidably mounted, a servovalve 23 having three spaced lands. The servovalve is loaded in the same direction as the piston 19 by means of a coiled compression spring 24 one end of which bears upon the servovalve and the other end of which bears upon the base portion of a cup-shaped member 25 slidable within the bore 22 of the piston and urged by the action of the coiled compression spring 24 into contact with a plug 26 which closes the adjacent end of the chamber which contains the piston.

Formed in the piston is a passage 27 which extends from the end thereof remote from the coiled compression spring and which breaks into the bore containing the servovalve at a first port 28. In the equilibrium position (as will be described) the first port 28 is closed by the center land 23a of the servovalve. The groove on the side of the center land 230 which is remote from the coiled compression spring 24 is in communication by way of a passage 29 formed in the piston and a cooperating passage 30 in the surrounding body part, with fluid under pressure. Conveniently and as shown this fluid is derived from the outlet 7 of the feed pump although any other source of fluid under pressure may be utilized such for instance as the oil pump of the associated engine. The groove on the opposite side of the center land 23a is in communication by way of a passage 31 formed within the piston and a passage 32 in the body part, with a drain. This drain may be the usual drain which is to be found in this form of pumping apparatus or alternatively it may be the inlet of the feed pump. In addition, the end of the chamber containing the spring which loads the piston is also in communication with the drain.

A further passage 33 formed in the piston and a cooperating passage 34 in the body part communicates with the outlet 7 of the feed pump so that the pressure of fuel delivered by the feed pump is applied to the end of the servovalve 23 to move it in opposition to the action of the coiled compression spring in operation, as the output pressure of the feed pump varies, the servovalve moves in the appropriate direction and the port 28 is uncovered to one or the other of the grooves of the servovalve. If the pressure is increasing the port 28 is uncovered to the groove which is in communication with the passage 29 and when this occurs fluid under pressure flows through the port and the piston is moved in opposition to the action of its spring. Eventually an equilibrium position is achieved in which the port 28 is again closed by the center land 23a. In the event that the output pressure of the feed pump decreases then the port 28 will be uncovered to the groove which is in communication with the passage 31 and fuel will flow through the port to the drain and thereby the piston will move under the action of its spring until the first port is again covered by the center land 23a of the servovalve.

It is desireable that the timing of injection of fuel to the engine should be varied in accordance with the load applied to the engine. The load applied to the engine or in other words the power developed by the engine is dependent upon quantity of fuel supplied to the engine and this is determined by the setting of the throttle 14. In order to achieve variation in the timing in accordance with the load applied to the engine with the present apparatus, a passage 35 is provided in the piston 19 and this cooperates with a passage 36 in the body part. The passage 35 breaks into the bore 22 containing the servovalve so that fluid pressure can act upon the servovalve to assist the action of the coiled compression spring 24.

In order to isolate the pressure in the passage 35 from the drain pressure acup-shaped part 24a is provided and which is slidable within the bore 22 relative to the piston 19. The operation of the apparatus is exactly as described except that the servovalve is now responsive to two fluid pressures as well a as the force exerted by the coiled compression spring 24.

' The pressure of fuel within the passage 35 is controlled as shown in FIG. 4 by a variable orifice 37 defined by the throttle .valve 14. The fuel pressure upstream of the variable orifice is derived from the outlet of the feed pump and means is pro- ,vided for maintaining the pressure upstream of the variable orifice substantially constant. As shown this means may take the form of a restriction 38 disposed intermediate the variable orifice and the outlet of the feed pump and a constant pressure valve 39 for maintaining the pressure intermediate the restriction and the variable orifice, substantially constant. The downstream side of the variable orifice is connected to the passage 36 and a restrictor 40 is provided in a branch passage which communicates with the drain. Adjustment of the throttle varies the effective size of the variable orifice and thereby ,the pressure which is applied through to the servovalve.

lclaim: 1..A liquid fuel pumping apparatus for supplying fuel to infinal combustions and comprising an injection pump, a member adjustable to control the timing of injection of fuel to thexngine, a fluid pressure operable piston contained within a cylinder, means connecting said piston to said member so that movement of the piston will efi'ect adjustment of said member, an end closure for the cylinder, a coiled compression spring acting between the piston and said end closure, said spring acting to urge the piston towards one end of the cylinder, a bore formed in said piston, a servovalve slidable in said bore for controlling the fluid pressure applied to the piston at its end remote from its spring, a further spring acting on the servovalve, passage means through which a first fluid pressure can be admitted to the bore so as to act on the servovalve in opposition to its spring, the magnitude of said first fluid pres sure being dependent upon the speed at which the apparatus is driven, a part slidable in the open end at the bore and which is loaded against said end closure by the action of the further spring, and further passage means for admitting a second fluid pressure to the bore so as to act on the servovalve to assist the action of its spring, the magnitude of said second fluid pressure being dependent upon the load applied to the engine and the part serving to prevent said second fluid pressure from acting on the piston. 

1. A liquid fuel pumping apparatus for supplying fuel to internal combustions and comprising an injection pump, a member adjustable to control the timing of injection of fuel to the engine, a fluid pressure operable piston contained within a cylinder, means connecting said piston to said member so that movement of the piston will effect adjustment of said member, an end closure for the cylinder, a coiled compression spring acting between the piston and said end closure, said spring acting to urge the piston towards one end of the cylinder, a bore formed in said piston, a servovalve slidable in said bore for controlling the fluid pressure applied to the piston at its end remote from its spring, a further spring acting on the servovalve, passage means through which a first fluid pressure can be admitted to the bore so as to act on the servovalve in opposition to its spring, the magnitude of said first fluid pressure being dependent upon the speed at which the apparatus is driven, a part slidable in the open end at the bore and which is loaded against said end closure by the action of the further spring, and further passage means for admitting a second fluid pressure to the bore so as to act on the servovalve to assist the acTion of its spring, the magnitude of said second fluid pressure being dependent upon the load applied to the engine and the part serving to prevent said second fluid pressure from acting on the piston. 